Super high gas separation performance membranes derived from a brominated alternative PIM by thermal induced crosslinking and carbonization at low temperature

In carbon dioxide capture and sequestration, achieving excellent performance, robustness, and reliability of gas separation membranes is a big challenge. Here, we report two novel highly crosslinked and partially carbonized molecular sieve membranes (CCMSM) that partially achieve the above goals for the first time. By thermally treating a novel bromomethyl substituted alternative intrinsic microporous polymer at relatively low temperatures of 340 °C and 350 °C, two PIM-BA-340 and PIM-BA-350 CCMSMs were obtained. They underwent the mechanism of triazine crosslinking (type I), debromomethylation induced crosslinking (type II) and partial carbonization (type III), resulting in membranes with excellent solvent resistance, thermal stability, and good mechanical strength. The PIM-BA-350 demonstrates a very small (4.1 Å) and intensive ultra-micropore (65.2%), consequently, outstanding gas separation property that outperformed various updated trade-off curves. The permeability of O2 is 145 Barrer and O2/N2 selectivity is 10.8, and further reaches unprecedented 22.2 at −20 °C. Additionally, PIM-BA-350 also shows remarkable CO2/CH4 separation property with CO2 permeability of 619 Barrer and CO2/CH4 selectivity of 124, even at a CO2/CH4 mixed-gas feeding pressure of 550 psi, there is no plasticization, and the selectivity for CO2/CH4 still reaches 106 coupled with a CO2 permeability of 306 Barrer. This low temperature formation of CCMSM paves a new path in searching for advanced membranes, and offers a great perspective in O2 and CO2 based industrial applications.